Upper and lower limb muscles in patients with...
Transcript of Upper and lower limb muscles in patients with...
Upper and lower limb muscles in patients with COPD: similarities in muscle
efficiency but differences in fatigue resistance
Eduardo Foschini Miranda, PT, MSc, Carla Malaguti, PT, PhD, Paulo Henrique
Marchetti, PhD, Simone Dal Corso, PT, PhD
Eduardo Foschini Miranda, Post-Graduate Program in Rehabilitation Sciences, Nove
de Julho University, São Paulo, Brazil
Carla Malaguti, Federal University of Juiz de Fora, Minas Gerais, Brazil
Paulo H. Marchetti, Post-Graduate Program in Human Performance, Methodist
University of Piracicaba, São Paulo, Brazil
Simone Dal Corso, Post-Graduate Program in Rehabilitation Sciences, Nove de Julho
University, São Paulo, Brazil
EFM received a master scholarship from the São Paulo Research Foundation
(FAPESP), Brazil.
Correspondence to: Simone Dal Corso, Postgraduate Program in Rehabilitation
Sciences, Universidade Nove de Julho – UNINOVE. Rua Vergueiro, 235/249 – 2o
subsolo, Bairro Liberdade, São Paulo/SP, CEP 01504-001, Brazil. Tel/fax: +55 11
33859241, email: [email protected]
[There are no conflicts of interest among authors and all participants signed a consent
form approved by the Ethical committee of Universida Nove de Julho - UNINOVE.]
RESPIRATORY CARE Paper in Press. Published on June 25, 2013 as DOI: 10.4187/respcare.02439
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Abstract
Background: Peripheral muscle dysfunction is a common finding in patients with
chronic obstructive pulmonary disease (COPD); however, the structural adaptation and
functional impairment of the upper and lower limb muscles do not seem to be
homogenous. Objective: To compare muscle fatigue and recovery time between two
representative muscles of the upper limb (middle deltoid, MD) and lower limb
(quadriceps femoris, QF). Methods: Twenty-one patients with COPD (with forced
expiratory volume in 1 s of 46.1 ± 10.3% predicted) underwent maximal voluntary
isometric contraction (MVIC) and an endurance test (ET, 60% MIVC) to the limit of
tolerance. The MVIC was repeated after 10 minutes, 30 minutes, 60 minutes and 24
hours for both the QF and MD. Surface electromyography was recorded throughout the
ET. Results: A significant fall in MVIC was observed only for the MD between ten and
sixty minutes after the ET. A significant increase of the root mean square and a greater
decline in median frequency throughout the ET occurred for the MD compared with the
QF. When dyspnea and fatigue scores were corrected by endurance time, higher values
were observed for MD (0.07 and 0.08, respectively) in relation to QF (0.02 and 0.03,
respectively). Conclusion: Patients with COPD presented a higher fatigability of a
representative upper limb muscle (MD) compared with a lower limb muscle (QF).
Keywords: COPD; muscle fatigue; electromyography; upper limbs; lower limbs
RESPIRATORY CARE Paper in Press. Published on June 25, 2013 as DOI: 10.4187/respcare.02439
Copyright (C) 2013 Daedalus Enterprises Epub ahead of print papers have been peer-reviewed and accepted for publication but are posted before being copy edited
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Introduction
It is well established that patients with chronic obstructive pulmonary disease
(COPD) present impaired skeletal muscle function, which plays a role in reducing
exercise tolerance1. Although the impairment of lower limb (LL) muscles are largely
responsible for limitations in activities such as walking and climbing stairs, it is known
that activities of daily living (ADL) performed with upper limbs (UL), especially
unsupported, are also poorly tolerated by patients with COPD2.
Although reduced skeletal muscle function has been reported in both the lower
limbs and the shoulder girdle muscles of patients with COPD, it has been speculated
that the metabolic and structural adaptations differ among LL and UL muscles3. For LL,
the quadriceps femoris (QF) is the peripheral muscle most commonly tested in COPD4.
Abnormalities of this muscle include1 reduced muscle mass, strength, endurance,
oxidative enzymes, proportion of type I fibers, augmentation of the proportion of type II
fibers, and decreased cross-sectional area of type I, IIa, and IIab fibers. These changes
increase the fatigability of the QF, which has been demonstrated in both dynamic5,6 and
isometric contractions7.
For UL, a variety of muscles has been studied, making it difficult to generalize
UL performance results2,8. Because of the finding that the isometric handgrip force is
conserved in patients with COPD, some studies infer that the upper limb function is
preserved9-11
. It appears that oxidative capacity is preserved or even increased in the
deltoid muscles of patients with COPD9, as opposed to what is observed in lower limb
muscles. One possible explanations for this difference is that patients continue to
perform, to a certain extent, the ADLs that involve the upper limbs but reduce their
performance of the activities that involve the lower limbs, adopting a sedentary lifestyle
in order to minimize dyspnea. That finding was prevalent in patients with severe COPD.
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However, patients present higher metabolic and ventilatory demand when performing
activities involving unsupported arm elevation with important dyspnea12-14
. In this
context, the middle deltoid (MD) is directly involved in all ADLs with upper limbs,
especially those that require elevation of shoulders. It is interesting to note that, unlike
the QF, it seems that the MD has a multi-mode fibre distribution, i.e., normal, atrophic
and hypertrofic sizes15, which could influence the development of muscle fatigue when
performing ADLs with upper limbs.
Few studies have compared LL and UL muscle function4,16-19
. Some studies
support a greater impairment of LL10,17,19
in relation to the UL muscles, as patients
reduce physical activities in daily life using the LL20, thus preserving UL activities. On
the other hand, studies have shown that the muscle impairment between the upper and
lower limbs muscles is similar18, with comparable mechanical efficiency
17.
Due to ongoing controversy about the muscle impairment distribution between
LL and UL, this study was undertaken (1) to contrast the muscle fatigue between two
representative muscles of the lower (QF) and upper (middle deltoid, MD) limbs by
analyzing electromyographic changes at equivalent workloads and (2) to compare the
recovery time of muscle fatigue.
Material and methods
We studied 21 consecutive patients from the outpatient clinic of Nove de Julho
University. The inclusion criteria were clinical diagnosis of COPD and clinical stability
(no change in medication dosage in the preceding four weeks or during the study). The
exclusion criteria were presence of cardiac, orthopedic, and neurological diseases.
Informed consent was obtained from all patients prior to their inclusion in the study.
This study was approved by the institutional ethics committee.
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Study design
This was a prospective, cross-sectional study performed in two visits (24 hours
apart). The subjects were assessed at the same time of day (between 2:00 and 3:00 pm),
and they were instructed to refrain from any strenuous activities in the 72h before the
procedure. After study enrollment, the patients were randomized to determine the order
of evaluation of the muscles (QF and MD or MD and QF). On the first visit, the patients
underwent the following sequence of tests: (1) maximum voluntary isometric
contraction (MVIC), (2) an isometric endurance test (60% of the MVIC) to the limit of
tolerance, and (3) repetition of MVIC after 10 minutes, 30 minutes, 60 minutes and 24
hours later. Then, the other muscle was evaluated in the same sequence. At the second
visit, the patients underwent MVIC of QF and MD to compare the recovery time of
muscle fatigue. All measurements were made with electromyographic recording. There
was a rest period of five minutes between sequences 1 and 2.
Spirometry
Spirometric tests were performed using a CPFS/D USB (Medical Graphics
Corporation®, St. Paul, MN). The subjects completed at least three acceptable maximal
forced expiratory maneuvers, according to acceptability and reproducibility ATS/ERS
criteria21. The following variables were recorded: FVC, FEV1, and FEV1/FVC. The data
were expressed in absolute values and in predicted percentage22.
Skeletal muscle function assessment
The strength of the QF was obtained on the dominant leg by MVIC. This
measurement was taken with the subject seated on a leg extension chair (Carci®, São
Paulo, Brazil) at 60° knee flexion. A non-elastic strap connected the ankle to a load cell
RESPIRATORY CARE Paper in Press. Published on June 25, 2013 as DOI: 10.4187/respcare.02439
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(EMG System model EMG800C, São José dos Campos, Brazil) that was interfaced to a
computer for MVIC recording. A strap was also placed across the patient’s pelvis to
minimize hip movement during the tests. The patients performed three repetitions of
MVIC of the knee extensors, each one maintained for 5s, with a minute of rest between
them. The highest value from the three reproducible contractions (<5% variability
among attempts) was considered for analysis23.
After a rest period of 5 min, endurance of the QF was evaluated by the isometric
endurance test, at 60% of the MVIC, to the limit of tolerance (Tlim)23. A visual
reference mark corresponding to the submaximal workload was shown on a computer
screen in front of the subject for visual feedback. In addition, during whole test verbal
encouragement was given for the patient maintain contraction as long as possible. The
isometric endurance test stopped when a 20% drop of the produced force occurred.
The MVIC of the MD of the dominant arm was measured with the patient seated
on a chair. The shoulder was placed at 90° abduction, with the elbow extended and the
palm of the hand facing up. This level of shoulder elevation was chosen because it is a
common position for several ADLs performed with the UL. A load cell was attached
with a strap to the wrist of the patient’s dominant arm. Following the same sequence
used in the QF assessment, the patients first performed three brief (5s) reproducible
MVIC s of the MD, with a minute of rest between them. Again, the highest value was
considered for analysis. Then, the patients sustained a submaximal isometric contraction
(SIC) against 60% of the MVIC, to the Tlim. Visual feedback was provided on the
computer screen during all measurements.
Scores for dyspnea and leg (QF) and arm (MD) fatigue, before and after
endurance tests, were assessed by the modified Borg scale24. Dyspnea and fatigue scores
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were corrected for endurance time in order to adjust the perception of effort for work
performed by each muscle.
Surface electromyography recording
Surface electromyography (sEMG) signals were recorded (EMG System, model
EMG800C, Sao José dos Campos, Brazil) during the MVIC, SIC, and endurance tests.
The sEMG signals were also recorded with a preamplifier (gain 1,000x), common mode
rejection >-85 dB. The participants’ skin was prepared before placement of the EMG
electrodes by shaving the hair at the site of electrode placement and cleaning the skin
with alcohol. Bipolar passive disposable dual Ag/AgCl snap electrodes (1cm diameter)
for each circular conductive area, with 2cm center-to-center spacing, were placed over
the longitudinal axes of the QF and MD in the direction of the muscle fiber, according
to the SENIAM/ISEKI protocol25. A ground electrode was placed on the contralateral
elbow. The sampling frequency was 1000 Hz26. The criterion adopted to normalize the
sEMG data was the MVIC. Then, the digitized sEMG data were first band-pass filtered
at 20–400 Hz, using a fourth order Butterworth filter with zero lag. For the temporal
analysis, the amplitude of the sEMG signals was expressed as RMS (1s moving
window) and normalized by MVIC. For the time-frequency analysis, sEMG data were
analyzed with a short-time Fourier transform applied to 1s epochs. The median
frequency (MF) of the spectrum for each epoch was computed, and the linear regression
of the median frequencies versus time was determined. The slope of the straight line
(indicating the rate of frequency change per second) was adopted as a second index of
fatigue27-29
. All data were analyzed using a customized program written in MATLAB
(Math Works Inc., Natick, MA). The MVIC was corrected by muscle mass.
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Body composition assessment
Body mass index
Body mass index (BMI) was calculated as weight/height2 (kg/m
2). Body weight
was assessed with a beam scale to the nearest 0.1 kg, with subjects standing barefoot
and in light clothing. Body height was determined to the nearest 0.1 cm with subjects
standing barefoot.
Estimation of mid-arm muscle area
The mid-arm muscle area (AMA) was estimated using the following equation:
AMA = mid-arm circumference, cm - (0.314 x triceps skinfold, cm)2 / (4 x 3.14)
30. The
mid-arm circumference was measured at the midpoint of the arm, between the tip of the
acromion and the olecranon process, with a steel tape with the arm relaxed and parallel
to the trunk. A skinfold caliper (Lange®, Cambridge, MD) was used to measure the
triceps skinfold, which was taken over the triceps muscle, halfway between the elbow
and acromial process of the scapula31. The unit was expressed in cm
2.
Estimation of mid-thigh muscle area
To estimate the mid-thigh muscle area (TMA), mid-thigh circumference (MTC)
and anterior thigh skinfold (ATS) were taken midway between the inguinal crease and
the top of the patella, with the patient standing with feet shoulder-width apart. The same
steel tape and skinfold caliper were used as for the AMA. The TMA was obtained as
follows: TMA = mid-arm thigh, cm - (0.314 x anterior thigh skinfold, cm)2 / (4 x
3.14)32. The unit was expressed in cm
2.
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Statistical analysis
Based on the results from the five first patients, we obtained a standard deviation
(SD) for MF of 8 Hz and a difference of 7 Hz between the pre- and post-endurance test.
Assuming a type I error of 0.05 and a type II error of 0.2, the sample size resulted in 21
patients with COPD. The normal distribution of data was verified by the Kolmogorov–
Smirnov test. The variables (age, BMI, muscle area for MD and QF, lung function, and
Borg scores for dyspnea and fatigue) were expressed as mean and SD by presenting a
parametric distribution. Changes in variables (MVIC, RMS, and MF) over time were
analyzed by repeated-measures analysis of variance. Linear regression analysis over
time was applied to rate of change of MF to obtain the slope of the regression line. The
level of significance was set at P < 0.05.
Results
Baseline characteristics of the 21 patients (two women) are shown in Table 1.
According to the GOLD criteria, most of the patients (n = 15) presented severe
obstruction, and the six remaining patients had moderate obstruction.
Insert Table 1
Table 2 shows the variables obtained from the strength and endurance tests. MD
showed reduced MVIC compared to QF (P < 0.05). However, no significant difference
was observed when MVIC was corrected for muscle mass, but we found statistical
difference for the limit of tolerance in the endurance test corrected for the maximal
voluntary isometric contraction (P < 0.05). The submaximal workload performed by
MD was lower than that of QF. Although the same MVIC percentage (60%) for the
endurance test was used for both muscles, the endurance time for MD was about 40% of
that performed by QF (Figure 1).
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Insert Table 2
Insert Figure 1
A significant drop in MVIC was observed in MD, at 10 and 60 minutes, but not
30 min and 24h after the endurance test (Figure 2).
Insert Figure 2
Figure 3A shows a significant increase in RMS of MD compared to QF only in
25% of endurance test (% duration). Figure 3B shows a greater decline in MF
throughout the endurance test for MD compared to QF.
Insert Figure 3
There was a significant difference in the slope of the MF over time between MD
and QF (-3.77 ± 1.4 and -2.68 ± 1.2, respectively; p < 0.03).
In relation to perceived exertion, the majority of the patients stopped the
endurance test due to local muscle fatigue (MD: 18 patients and QF: 16 patients), and
three patients presented higher scores of dyspnea for MD and five patients for QF.
Ratings of perceived exertion for dyspnea and fatigue increased significantly for QF
(from 1.3 ± 0.8 to 2.1 ± 1.2 and 1.3 ± 1.0 to 2.8 ± 1.3, respectively) and MD (from 1.4 ±
0.9 to 2.7 ± 1.9 and 1.6 ± 1.1 to 3.2 ± 1.7, respectively). When dyspnea and fatigue
scores were corrected for endurance time, higher values of this index were observed for
MD (0.07 and 0.08, respectively) compared to QF (0.02 and 0.03, respectively) (P
<0.05).
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Discussion
This study compared fatigue between two representative muscles of the upper
and lower limbs in patients with COPD. The main finding is that, despite similar muscle
efficiency, muscle fatigue was evident earlier and was more pronounced in the MD.
The lower muscle strength presented by MD compared to QF was expected.
Similar results have been showed for the biceps brachii (BB) in relation to QF18.
Although Gosker et al18 have measured the fat free mass, muscular strength has not
been corrected for muscle mass, which reflects the efficiency of muscle. In this context,
in our study, the difference observed in muscle strength between MD and QF
disappeared after correcting them for the respective muscle mass. Therefore, muscle
efficiency was similar between MD and QF, indicating that the contractile apparatus
was preserved19. Then, the difference in endurance time between MD and QF suggests
that neither strength nor muscle mass would be a determinant of muscle endurance.
The reduction of muscular endurance, regardless of loss of muscle mass, in
patients with COPD has been related to intrinsic muscular alterations, such as reduction
of type I fibers and reduced oxidative enzyme activity1. Consequently, there is a
predominance of anaerobic metabolism, resulting in early lactate accumulation and
muscle fatigue. In absolute values, the dyspnea and fatigue scores were similar at the
peak of both endurance tests. However, the endurance time was lower for MD than for
QF (Table 2). When corrected for the endurance time, i.e. work performed, dyspnoea
and fatigue, in fact, were superior for MD compared to QF. Local muscle fatigue
possibly occurred due to increased lactate production per unit of muscle mass. A
possible mechanism related to dyspnea is the change in lung volume during the UL
activities, characterized by decreased forced vital capacity, increased functional residual
capacity, and inspiratory capacity decrease12,33
. In addition to the changes in lung
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mechanics, it is speculated that reduction of blood flow during elevation of the UL leads
to increased production of lactate, which increases ventilation demand and,
consequently, dyspnea34,35
.
One of the most common methods used to quantify the development of muscle
fatigue is the decline in maximum strength36. In our study, a greater drop in strength
was observed for the MD compared to the QF (Figure 1). This result is similar to that
found by Gosker et al.16; however, the magnitude of the reduction in strength was lower
in our study in both muscles (MD: 20.6% and QF: 10.6%) when compared to the study
of Gosker et al.16 (BB: 42% and QF: 28%). The larger decline in strength observed in
the study of Gosker et al.16 may be attributed to a more intense fatigue-inducing
protocol (i.e., 15 sequential maximal voluntary contractions at an angular velocity of
90° s), as well as to differences in disease severity compared to our patients (FEV1: 32 ±
11% vs. 46 ± 10%, respectively) and the fat free mass and the strength was also lower in
patients than control subjects.
Several studies have evaluated QF fatigability after cycling, walking, repeated
maximum voluntary contractions, and local endurance tests37-39
. However, to the best of
our knowledge, only our study has analyzed the recovery time of fatigue for UL after a
fatigue-inducing protocol. In addition to the greater decrease in strength compared to
the QF, MD presented longer recovery time of the baseline MVIC. Beyond smaller
muscle mass, this finding may be explained by the dual function of the accessory
respiratory muscles during unsupported arm exercise, ventilation, and postural
maintenance, which can contribute to more pronounced fatigue15. Unlike that observed
in the lower limb muscles, alterations in fiber-type distribution and decreased metabolic
capacity do not seem to be involved in early fatigue of the upper limb muscles. This
assertion is based on previous studies that demonstrated preserved or even increased
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oxidative capacity7, as well as a concomitant presence of the normal, atrophic, and
hypertrophic pattern of fibers within the MD when compare to control group15.
Although widely used for evaluation of muscle fatigue, submaximal sustained
isometric contraction40-44
has the disadvantage of being dependent on motivation.
However, we associate the use of electromyography during the tests which resulted in a
more objective evaluation of muscle fatigue. In this context, a 4% decrease in MF has
been recommended as an indirect marker of contractile fatigue evaluated by sEMG45.
Therefore, while our patients certainly presented muscle fatigue for both QF and MD, it
was more pronounced in the MD, as seen in the higher slope in the MF over time
(Figure 2B). This data can not be directly compared with other studies in patients with
COPD because we are unable to find any study that has analyzed it. Comparing with
healthy subjects46, a more pronounced drop in the slope of the MF over time was
observed in our patients (-0.67 vs. -3.77, respectively). It is worth noting that even in
healthy subjects (61 ± 6 years old) performing ADL with unsupported arm elevation,
Panka et al47 found changes in breathing pattern and greater activation of the
sternocleidomastoid.
This study had some limitations. Muscle fatigue was evaluated by volitional
measurements (MVIC and endurance time); however, we used outcomes from sEMG in
order to confirm the muscle fatigue. The results found in our study cannot be
extrapolated to other body positions such as standing position. The lower and upper
limb muscle mass were estimated, but the measures used in our study have traditionally
been used in the literature30,48
. A huge variability was observed for Tlim for MD. Our
patients did not undergo muscle biopsy, but previous study has identified three patterns
of muscle composition of deltoid in COPD15: normal sized fibres, atrophic fibres and
hypertrofic fibres. Then, we speculated that the patients who presented with higher
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endurance time probably had a predominance of normal sized fibers and/or hypertrophic
fibres, while those with less endurance time could have a pattern of atrophic fibers.
Currently resistance training is one of the components of the pulmonary
rehabilitation program for patients with COPD. Based on our findings, we suggest that
training the upper limbs in patients with COPD should be accomplished with high
repetition/low resistance to increase muscular endurance. Further studies measuring
pulmonary gas exchange while patients perform a fatigue-inducing protocol should be
conducted to verify whether changes in electromyography outcomes reflect higher
oxygen consumption, carbon dioxide production, and ventilation. In addition, studies
evaluating lung volume, especially inspiratory capacity, could help to explain the
increased perception of dyspnea observed in the upper limb endurance tests.
In conclusion, we have found that patients with COPD presented with higher
fatigability of upper limb muscle compared to lower limb muscle with longer recovery
time.
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Table 1 – Subjects characteristics.
Variables Mean ± SD
Age, years 70 ± 10.2
BMI, kg/m2 25.5 ± 5.2
Arm muscle area, cm2 49.7 ± 18.9
Thigh muscle area, cm2 128.8 ± 32.6
FVC, L (% pred) 2.2 ± 0.8 (68.2 ± 16.8)
FEV1, L (% pred) 1.1 ± 0.3 (46.1 ± 10.3)
FEV1/FVC ratio, % 58.7 ± 12.9
BMI: body mass index; FVC: forced vital capacity; FEV1: forced expiratory volume in
one second in liters and in percentage of predicted; L (% predicted): in liters and in
percentage of predicted.
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Table 2 – Data from tests of muscle strength and endurance.
Variables MD QF
MVIC (kg) 6.7 ± 2.5 16.0 ± 5.2 *
MVIC/muscle mass 0.15 ± 0.05 0.13 ± 0.05
Load of endurance test (kg) 4.0 ± 1.6 9.8 ± 3.1 *
Tlim (s) 49.6 ± 39.2 127.1 ± 76.5 *
Tlim/load endurance test (s/kg) 13 ± 9 15 ± 12 *
MVIC: maximal voluntary isometric contraction; kg: kilograms; s: seconds; Tlim: limit
of tolerance of the endurance test; Tlim/MVIC: limit of tolerance of the endurance test
corrected for the maximal voluntary isometric contraction *P < 0.05.
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Figure 1- Endurance time for MD and QF. Open circles correspond to outliers.
QFMD
400
300
200
100
0
Endurance time, sec
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60
80
100
120
Basal 10min 30min 60min 24h
Strength (% basal)
Figure 2 – Changes in MVIC for QF (solid circles) and MD (open circles). * P < 0.05 in
relation to basal for MD.
* *
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Figure 3 – Changes in RMS (A) and MF (B), expressed in percentage of baseline
values, for QF (solid circles) and MD (open circles). * P < 0.05 compared to baseline
values and among exercise time (% duration) for both muscles. † P < 0.05 for
comparison between QF e MD.
95
100
105
110
RM
S (
% b
aselin
e v
alu
e)
80
90
100
110
Basal 25% 50% 75% 100%
Endurance test (% duration)
Me
dia
n fre
que
ncy
(% b
aselin
e v
alu
e)
*
*†
*
*†
*
* *
*
*
*
*
*
*
*
*
†
A
B
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